We report the biomimetic synthesis of polyethylene glycol (PEG) grafted silica nanoplates templated by double hydrophilic PEG-b-poly-L-lysine diblock copolymers. The silica nanoplates can be re-dispersed in PEG selective solvents. The sizes of silica nanoplates can be tuned from a few hundred nanometers to tens of micrometers.